DE102018103893A1 - Variable stiffness object - Google Patents

Abstract

The variable rigidity object (10) has at least two foils (14, 16) which are arranged one above the other and have inner sides (18) facing one another and outer sides (19) facing away from one another. The distance between the two foils (14, 16) can be changed by generating a negative pressure within an inner volume located between the two foils (14, 16) and / or by generating an overpressure in an outer volume located outside the foils (14, 16). On the inside (18) of each film (14, 16) there is a surface structure (22) of an array of a plurality of raised projections (12) fixed on the inside (18) of the film (14, 16) with between them arranged intermediate spaces (20) which are each surrounded by at least three projections (12) arranged and / or formed. A projection (12) of the surface structure (22) on the inner side (18) of the one film (14, 16) dips into the associated intermediate space (20) of the surface structure (22) when the distance between the two films (14, 16) is reduced. on the inner side (18) of the other film (14, 16), such projection (12) being provided on at least three of the intermediate space (20) bounding projections (12) of the surface structure (22) of the inner side (18) of the other film (14,16) is present.

Description

The invention relates to an object with variable rigidity, considered by itself as a construction element of a device or as a semi-finished for stiffening a device or part of a device as needed.

In particular, the invention relates to a mechanical structure by means of which the rigidity of an object can be altered instantaneously, reversibly and at will, and indeed in a first state the object is almost arbitrarily flexible and in a second state significantly more rigid. In intermediate states, the object can assume degrees of intermediate flexibility or intermediate stiffness. These statements apply to a continuous amount of bending axes / bending edges along the object or axes / edges through the object. An example is a cuboid object with a high base area and low height, such as a windshield, which is bent along a horizontal bending axis. The stiffness along such a bend can now be changed between two states, regardless of where the object is bent.

• - hohe Sicherheit und Stabilität. Kollidiert ein Mensch mit diesem Objekt, so verformt sich das Material und entzieht dem Aufprall hierdurch Energie. Der Aufprall wirkt weicher, die Verletzungsgefahr sinkt. Die Kraft wird ebenfalls abgefedert, sodass eine geringere Maximalkraft übertragen wird. Hierdurch werden Bauteile wie Servomotoren, welche über eine Feder mit einem Endeffektor verbunden sind, durch einen Aufprall mechanisch weniger belastet.
• - hohe Flexibilität und Adaption. Das Objekt kann sich seiner Umwelt anpassen. Hierdurch kann es in verschiedenen Umgebungen genutzt werden oder um Hindernisse herum bewegt werden. Zudem kann es die Kontaktfläche mit einem Objekt erhöhen, sodass z.B. elastische Haut eine höhere Reibung und damit eine stärkere Verbindung mit einem gegriffenen Gegenstand aufbauen kann.
• - hohe Energie-Effizienz (Resonanz). Bei einer spontan eintretenden Kraft speichert ein elastisch-nachgiebiges Objekt Energie. Diese kann es nutzen, um sich wieder abzustoßen. Kängurus speichern hierdurch bei Bodenkontakt Energie in ihren Muskeln und Sehnen und setzten sie beim Absprung wieder frei.
• - hohe Maximalkraft. Eine anliegende Kraft kann iterativ das Objekt verformen und so Energie in dem Objekt speichern. Zu einem gegebenen Zeitpunkt wird die Verformung wieder aufgelöst, wodurch kurzzeitig eine hohe Kraft entsteht, welche die ursächliche Kraft weit übersteigen kann.
• - viele Freiheitsgrade. Ein nachgiebiges Objekt kann an vielen Stelle verformt werden, wodurch es viele Bewegungen ermöglicht.

Generally, the stiffness of a material determines its deformation in response to an applied force or moment. A rigid material deforms little at a given force, while a material with a low rigidity at the same force has a great deformation. Depending on the application, a stiff or yielding material must be used, since both states have exclusive advantages. For example, a compliant object allows

• - high security and stability. If a person collides with this object, the material deforms and thereby deprives the impact of energy. The impact is softer, the risk of injury drops. The force is also cushioned, so that a lower maximum force is transmitted. As a result, components such as servomotors, which are connected via a spring with an end effector, mechanically less loaded by an impact.
• - high flexibility and adaptation. The object can adapt to its environment. This allows it to be used in different environments or to be moved around obstacles. In addition, it can increase the contact surface with an object, so that eg elastic skin can build up a higher friction and thus a stronger connection with a gripped object.
• - high energy efficiency (resonance). In a spontaneously occurring force stores an elastic-compliant object energy. This can use it to repel. Kangaroos thus store energy in their muscles and tendons when they come in contact with the ground, releasing them again when they jump off.
• - high maximum force. An applied force can iteratively deform the object and thus store energy in the object. At a given point in time, the deformation is dissolved again, resulting in a momentary high force, which can far exceed the causative force.
• - many degrees of freedom. A compliant object can be deformed in many places, allowing many movements.

In contrast, allows a stiff object, for example

• - efficient power transmission. If you exert a force on the object, it will be transmitted faster and with little or no loss of power.
• - high precision and simple models. The behavior of a stiff object requires much simpler models, its behavior is very predictable and therefore precise. This makes it easy to control the movements or forces to be exerted on the object.

Depending on the situation, the advantages of a yielding or stiff object predominate (see the application examples). For this reason, it is helpful to be able to greatly increase and decrease the rigidity of an object depending on the intended use. Ideally, this process should be executable, instantaneous, reliable, and reversible at any point in time.

In the following, known attempts to solve the above problem together with their specific problems will be described. Be listed problems that can be overcome by the invention.

Magneto and electrorheological materials

Magneto and electrorheological (MR, ER) materials change their mechanical properties upon application of a magnetic or electric field. These are mostly magnetically polarizable or dielectric particles which are dissolved in a liquid. In the absence of a field, they randomly disperse in the fluid. When a field is applied, the particles form chains and increase the viscosity of the liquid until they form a viscoelastic solid [1].

MR and ER materials usually require high electromagnetic field strengths. Moreover, they are primarily viscous and non-elastic, meaning they can generate mechanical energy only dissipate but not save. Moreover, the theoretical description of their properties is non-trivial, which makes their control difficult [2]. High rigidity is not achievable [3].

Thermorheological materials

Thermo-rheological materials exploit the phase transitions between different states of aggregation of materials resulting from altered temperatures [4]. The transition between ice and water is an example of this.

Temperature changes and the associated phase transitions usually take place very slowly. In addition, the material must be wrapped or traversed by relatively large equipment, which can heat and cool it. To produce and maintain a desired temperature, energy must be expended throughout. Producing a spatially focused temperature is also extremely difficult. Depending on the temperature range of the phase transition, there is also a considerable risk of injury due to combustion / frostbite, especially in the material-human interaction.

Granular jamming

Granular jamming describes the behavior of granular particles that are exposed to a vacuum in a vacuum-tight bag made of a flexible film. The vacuum creates a pressure difference between the external air pressure and the internal vacuum. This pressure difference pushes the particles together, which tilt / clump together. The more completely the vacuum generated, the more the particles tilt, which changes the behavior of the bag from that of a flexible liquid to that of a solid [7], [5]. The shape of the bag is not predetermined in the neutral configuration and may change as desired until the vacuum is applied. The vacuum fixes the last form.

Granular jamming requires a large volume of granular particles to achieve significant rigidity. In addition, the description of such objects is non-trivial, so that one can not predict the resulting stiffness to a given vacuum. Accordingly, granular jamming has not yet been used in applied technical systems [3].

Layer jamming

Layer Jamming also uses a bag in which a vacuum is built up. In the bag, layers of high friction materials are superimposed or interwoven. As long as there is no vacuum, the layers can easily slip past each other. As long as the layers are inherently compliant, the pouch is now yielding. As soon as a vacuum is applied, the layers are pressed together. You can then no longer slip past each other, the bag solidifies in its current form and has a much higher rigidity [3], [8]. This principle is used commercially by Tecnalia for the product Varstiff and is eg in WO 2011/079865 A1 and US 2015/0369325 A1 described.

Layer jamming is prone to contamination and fluid trapping within the bag, as the principle is based on friction. In addition, the layers rub against each other in the neutral state. This implies that the object is very viscous even in the neutral state, because the air bag contains many layers, which by definition have a high coefficient of friction. In addition, for theoretical reasons, Layer Jamming offers a strong limitation on maximum stiffness. Because on the one hand, it is limited by the coefficient of friction. On the other hand, even with an ideal connection (i.e., an infinite coefficient of friction), the stiffness of the vacuum bag would be at most equivalent to that of the layer material. These layers are pressed together and thus identical to a single layer with a higher thickness. In the neutral state, however, the bag can only be deformed if the layers themselves can also be deformed. Therefore, ideally, a material must be chosen, which itself is rather yielding. If the effective thickness of the object changes as a result of the vacuum, it becomes stiffer, but remains basically yielding.

Tooth-Linked Vacuum Pressure Locking Mechanism

Zou et al. [6], [9] developed a mechanism that also uses the pressure difference between the normal air pressure and the artificial air pressure inside a flexible bag. They use a flexible hose, which is surrounded by grooves. This is in turn surrounded by an air-impermeable film with individual teeth. Hose and foil together form the air-impermeable bag. If a vacuum is now generated, the outer foil presses against the tube, the teeth are pressed into the grooves of the tube. If you want to bend the hose now, you would have to stretch the film. As long as the film is not stretchable, the tube is now rigidly fixed in its current form.

A disadvantage of the mechanism is that it is only on tubular structures can be applied. An extension to flat objects is not described and not trivially possible.

The stability of the object is limited by the fact that foil and tube determine the stiffness in the neutral state as well as in the state of negative pressure. Therefore, the film should be rather thin, so that the object is slightly bent in the neutral state. In the state of negative pressure, the film is now pressed tightly against the large surface of the grooves. Adapting to the shape of the grooves creates a high pressure on the film, which can cause tearing and destroying the required vacuum. In addition, the film will not be able to completely nestle into the grooves. Pressure at these points can thus also bring the film easily to tearing.

In addition, the apparatus in the state of negative pressure will not be completely stiff depending on the degree of bending of the hose. It is believed that the film is stretched in the condition of a straight tube. If the hose is bent, the film will hang limply on the side of the inner radius. If the foil and tube are now fixed together at certain points through the teeth, there are some spaces between two teeth where the foil is not taut on one side. These gaps can continue to bend so far.

Other known concepts for Vacuum Pressure Locking Mechanism are, for example, in WO 2016/100174 A1 and WO 2016/100182 A1 described.

The object of the invention is to further improve the known concepts for the selective stiffening of an object by a new mechanical structure.

• - mindestens zwei Folien, die übereinanderliegend angeordnet sind und einander zugewandte Innenseiten sowie einander abgewandten Außenseiten aufweisen,
• - wobei der Abstand der beiden Folien durch Erzeugung eines Unterdrucks innerhalb eines zwischen den beiden Folien befindlichen Innenvolumens und/oder durch Erzeugen eines Überdrucks in einem außerhalb der Folien befindlichen Außenvolumen veränderbar ist,
• - wobei an der Innenseite der ersten Folie eine erste Oberflächenstruktur aus einem ersten Array von einer Vielzahl von auf der Innenseite der ersten Folie fixierten, erhabenen ersten Vorsprüngen mit zwischen diesen angeordneten ersten Zwischenräumen, die jeweils von mehreren ersten Vorsprüngen umgeben sind, angeordnet und/oder ausgebildet ist,
• - wobei an der Innenseite der zweiten Folie eine zweite Oberflächenstruktur aus einem zweiten Array von einer Vielzahl von auf der Innenseite der zweiten Folie fixierten, erhabenen zweiten Vorsprüngen mit zwischen diesen angeordneten zweiten Zwischenräumen, die jeweils von mehreren zweiten Vorsprüngen umgeben sind, angeordnet und/oder ausgebildet ist und
• - wobei ein erster Vorsprung der ersten Oberflächenstruktur auf der Innenseite der ersten Folie bei Verringerung des Abstands beider Folien in den diesem ersten Vorsprung zugeordneten gegenüberliegenden zweiten Zwischenraum der zweiten Oberflächenstruktur auf der Innenseite der zweiten Folie eintaucht und dabei an mindestens einem der diesen zweiten Zwischenraum begrenzenden zweiten Vorsprünge, vorzugsweise an sämtlichen den zweiten Zwischenraum begrenzenden zweiten Vorsprünge) der zweiten Oberflächenstruktur der Innenseite der zweiten Folie (seitlich) und ggf. auch stirnseitig an der zweiten Folie anliegt.

To achieve this object, the invention provides an object with variable stiffness, which is flexible in the non-stiffened state along a plurality of bending axes or bending edges and can optionally be stiffened, the object of the invention is provided with

• at least two films, which are arranged one above the other and have inner sides facing each other and outer sides facing away from each other,
• wherein the distance of the two films is variable by generating a negative pressure within an inner volume located between the two films and / or by generating an overpressure in an outer volume located outside the films,
• - On the inside of the first film, a first surface structure of a first array of a plurality of fixed on the inside of the first film, raised first protrusions arranged between them first interspaces, which are each surrounded by a plurality of first protrusions arranged and / or is trained,
• - Wherein on the inside of the second film, a second surface structure of a second array of a plurality of fixed on the inside of the second film, raised second projections with arranged between these second spaces, each surrounded by a plurality of second projections, arranged and / or is trained and
• wherein a first projection of the first surface structure on the inner side of the first film is immersed in reducing the distance between the two foils in the opposing second intermediate space of the second surface structure assigned to this first projection on the inner side of the second film and thereby on at least one of the second space bounding this second gap Projections, preferably on all of the second gap bounding second projections) of the second surface structure of the inside of the second film (side) and possibly also on the front side abuts the second film.

According to the invention, it is analogously provided that the object has at least two flexible foils of, for example, plastic material, on whose mutually facing inner surfaces surface structures of individual projections or blocks are arranged or formed. The protrusions of the one surface structure form gaps which are assigned to the protrusions of the other surface structure and which are enclosed by protrusions in each case. The projections are formed, for example, as cubes or square cuboids in cross-section and arranged, for example, like a checkerboard or otherwise in an array form. Any other form of protrusions is also conceivable. Advantageously, the projections are geometrically equal. The protrusions of a surface structure may be the same or different from each other. The same can apply with advantage for the projections of the other surface structure. The geometry of the projections and the spaces may be equal or unequal per surface structure. Furthermore, it is advantageous if a projection of one surface structure is complementary to the shape of the intermediate space of the other surface structure assigned to it.

According to a further embodiment of the invention, each projection has an n-fold when viewing the inside of a film in extension of the normal on this inner side Having rotational symmetry, where n is greater than three or four or greater than six or greater than eight.

The invention is simple to carry out using projection forms which fulfill the mathematical conditions of a platonic tiling. Then exactly three possible tilings of a plane with regular polygons are possible, namely triangle, square and hexagon. In that regard, therefore, each projection has in particular a 3-fold, 4-fold or 6-fold rotational symmetry in the sense mentioned above. The projections for the Platonic tiling should have bevels on the edges and corners, so that a hook-free interlocking and moving apart of the projections of both films is more easily ensured.

If now the two films are arranged at a distance from each other, without the protrusions of the surface structure of a film are immersed in the interstices of the surface structure of the other film, the object is flexible, said flexibility ultimately and preferably determined solely by the material of the films themselves is. The farther the foils are moved towards each other, the farther the projections dip into spaces. This already limits the flexibility of the object within certain limits. The object is completely rigid when the projections are completely submerged in the spaces assigned to them. At the latest when the projections are completely immersed in the interspaces, they abut against at least one and preferably all of the respective space bounding projections of the respective other surface structure. In addition, the top of a projection may also abut the bottom of the gap, which is preferably formed by the film. The engagement prevents any bending of the object stiffened thereby, now the stiffness is defined by the material of the protrusions. This material should be much stiffer, ie have a much higher modulus of elasticity than the material of the films, which should also have a low Dehnbahrkeit.

The two films may be two separate layers or else a common layer, which is folded back along a line to form the two films and thus forms two superimposed film layers.

As already mentioned above, the projections can basically have almost any desired geometric shape. Preferably, the projections should have flat surface portions along their peripheral edges. The projections may have the same width over their height or taper to their upper free ends. Chamfers, so "broken" edges on the projections, are so far advantageous, as it is when dipping the projections in their associated spaces of the respective counter-foil not to hooks or the like. comes. In that regard, these "broken edges" act as inlet and insertion aids.

The arrangement and shape of the projections and spaces of the two surface structures are particularly complementary, but this need not necessarily apply to the entire areas of the surface structures. So z. B. at least one space or a small number of spaces remain free of projections of the other surface structure or be filled by projections in each case only partially.

In an advantageous embodiment of the invention it is provided that the distance of the projections of the surface structure of the inside of each film is at least equal to the height of the projections and that the projections of the surface structure of the inside of each film or per individual film have the same geometry.

In a further advantageous embodiment of the invention, it is provided that the projections of the surface structure of the inside of each film or per individual film are arranged regularly.

In an advantageous embodiment of the invention it is provided that each projection has a peripheral peripheral surface which projects at an angle of substantially 90 ° from the inside of the film and that a projection in the state in which it is immersed in its associated space, the peripheral surface of a projection bounding this gap, and preferably the peripheral surfaces of all these projections bounding this gap contacted.

In a further advantageous embodiment of the invention, it is provided that each projection has a peripheral peripheral surface with a plurality of adjacent planar surface portions, wherein each two adjacent planar surface portions form an inner angle of less than 180 °, and that a projection in the state in which he immersed him assigned space, contacted a surface portion of a gap surrounding this gap and preferably in each case a surface portion of all this gap bounding projections.

Further, in an advantageous embodiment of the invention, it is provided that a plurality of pairs of films are arranged one above the other from each of a first film and a second film, wherein the outer side a film of a film pair rests against the outside of a film of the adjacent film pair and both films are joined together, in particular glued.

In an advantageous embodiment, the invention is characterized by at least one third film, which is arranged between the first and the second film, wherein the at least one third film on its two main sides each have a surface structure of an array of a plurality of on the relevant main page of the third Foil fixed, raised projections with spaces between them, which are each surrounded by a plurality of projections, and wherein the respective surface structure of the at least one third film complementary to the respective surface structure of the respective main side of the third film opposite the inside of the first and second film or the opposite major side of another third film.

In a further advantageous embodiment of the invention, it is provided that the first and the second film each having an outer edge, along which the two films are gas-tightly connected to form a first bag, and that the bag with a closable opening for ventilation of the Inside volume of the bag is provided.

Further, according to one embodiment of the invention, it is provided that each first, second and, if present, third film has an outer edge, in each case adjacently arranged films are gas-tight to form a bag along its outer edges, and that each bag with a closable opening provided for ventilation of the bag.

However, at least two bags may also be arranged next to one another in overlapping relationship. This creates an elongated arrangement of individual bags that can be "stiffened" independently of each other. A construction provided with such a linear "bag arrangement" can thus be selectively stiffened in some areas. A 2D bag arrangement of overlapping juxtaposed bags is also feasible and could, if necessary, be stiffened zone-wise or, in general terms, zone-wise provided with different flexibility.

Description of the invention

As can be seen from the above, the invention is thus based on the principle of creating a negative pressure, for example inside a bag, which presses the upper and lower film together.

The pressing together of the films can also be done by negative pressure from outside a bag. For the negative pressure z. B. a suction pump or a standing with the interior of the bag in fluid communication pneumatic piston / cylinder unit for the exchange of gas from the bag into the unit and vice versa (possibly designed as a closed system). The (possibly repeated forward and backward) movement of the piston can be done manually or by motor. Depending on the application, it may be advantageous if the "compression" is done quite quickly. It is also conceivable if the air in the bag is introduced or sucked by mouth (eg in the application of the invention for objects that are used in leisure or sports, such as a back protector in winter sports such as skiing or snowbording).

The invention will be described below with reference to this embodiment, but is not limited to this embodiment. Thus, the films do not necessarily need to form a bag. Also, more than two films, namely, an upper, a lower and one or more middle films may be provided. The directional details on the film (e.g., vertical / horizontal) are hereafter indicated as if the two films were parallel and flat, i. horizontally, one above the other. The films have any thickness and stiffness, but should not be stretchy. Each film is covered over a large area with glued-on blocks of a second, very stiff material, such as e.g. Aluminum (while the films are for example made of plastic material that is flexible and non-stretchable). All blocks have the same height. The two films are connected airtight at the edges. They thus form an approximately two-dimensional object. The stiffness of this surface (more precisely: plate), i. the force needed to bend it along an axis is intended to instantaneously switch between the stiffness of the film and that of the blocks by applying a vacuum.

This should apply to any possible bending axis / bending edge. The axis can be any possible (not necessarily straight) line that extends from one side of the object to another.

The idea underlying the invention consists in the fact that, without negative pressure / slight overpressure (neutral state), the distance between the two films is so great that the blocks barely touch each other or not. Ideally, the distance of the sheets is greater than twice the height of the blocks, so that the blocks do not touch. On each slide, the blocks are positioned so far apart that the slide flexes without the blocks touching each other. If this air bag is bent, the stiffness is determined by the stiffness of the film. As soon as a negative pressure in the bag and / or an overpressure from the outside compresses the foils, the blocks of the two mutual foils come to lie directly next to one another (edge to edge). If the object is bent, the blocks now block each other (lock mechanism), and the rigidity of the object is determined by the high rigidity of the blocks. Unlike in the case of layer jamming, the stiffness in the neutral and stiff state is thus determined by different materials with arbitrarily different properties.

• - Jede Folie ist mit den Blöcken bedeckt.
• - Auf jeder einzelnen Folie berühren sich die Blöcke bei einer Verbiegung der Folie nicht oder erst bei einem hohen Biegewinkel. Um einen maximalen Verbiegewinkel zu erreichen, sind die Blöcke so weit voneinander entfernt wie sie selbst hoch sind. Wenn sie näher aneinander angeordnet sind, funktioniert der hier beschriebene Effekt weiterhin; allerdings kann man die Folie zwischen den beiden Blöcken lediglich um einen kleineren Winkel verbiegen. Es ist anzunehmen, dass ein geringfügig kleinerer Verbiegewinkel in den meisten Anwendungen keinen Nachteil darstellt, da die Folie großflächig mit Blöcken bedeckt ist und sich die Biegewinkel zwischen den einzelnen Blöcken addieren zu einem beliebig großen maximalen Verbiegewinkel des gesamten Objekts.

The arrangement of the blocks on the two films determines fundamentally the properties of the object. The arrangement of the blocks as well as the blocks themselves should fulfill several characteristics. Some properties should be met. Other properties are not necessary, but provide improved properties of the object. It is necessary that on the two slides the blocks are arranged so that the following properties are fulfilled:

• - Each slide is covered with the blocks.
• - On each individual film, the blocks do not touch each other at a bending of the film or only at a high bending angle. To achieve a maximum bend angle, the blocks are as far apart as they are high. If they are closer together, the effect described here will continue to work; however, one can only bend the film between the two blocks by a smaller angle. It can be assumed that a slightly smaller bending angle is not a disadvantage in most applications since the film is covered with blocks over a large area and the bending angles between the individual blocks add up to an arbitrarily large maximum bending angle of the entire object.

• - Legt man die Folien aufeinander, so passen die Blöcke ineinander, d.h. sie können nebeneinander angeordet werden, ohne dass die Folie gedehnt werden müsste.
• - Sobald die Folien übereinandergelegt werden, besitzt jeder Block nun mit Blöcken der anderen Folie Nachbarkanten, welche direkt anliegen. Verbiegt man das Objekt, so blockieren sich die Blöcke gegenseitig. Die Steifigkeit des Objekts ist äquivalent zur Steifigkeit der Blöcke.
• - Die Blöcke müssen nun einer Verbiegung des Objekts entgegenstehen, unabhängig von der Achse der Verbiegung. Sie stehen einer Verbiegung entgegen, wenn entweder auf einer Achse ein Block liegt, oder aber zwei Blöcke eine gemeinsame Kante besitzen. Auf jeder möglichen Verbiegeachse sollen nun möglichst viele (mindestens ein) Blöcke und Nachbarkanten liegen, die einer Verbiegung entlang dieser Kante entgegenstehen. Da die Folie nicht/schwer dehnbar ist, wird sich der Abstand zwischen zwei Blöcken auch bei einer Verbiegung entlang ihrer gemeinsamen Kante nicht erhöhen.
• - Durch die erfindungsgemäße Anordnung der Vorsprünge bzw. Blöcke hat jede Folie Biegerichtungen, entlang derer keine Blöcke bzw. Vorsprünge angeordnet sind. Diese Biegerichtungen bilden eine 2D-Vektorbasis, so dass man jede der beiden Folien in jede beliebige Richtung, nämlich längs jeder Biegerichtung, verbiegen kann.
• - Im Zustand der Kompression ordnen sich nach der Erfindung die Blöcke bzw. Vorsprünge der beiden gegenüberliegenden Folien derart an, dass sie sich in jede mögliche Biegerichtung blockieren.

The characteristic described in this point means that each film is therefore yielding on its own. If the foils are sufficiently far apart, the stiffness of the entire object is equivalent to the stiffness of the foils.

• - Laying the slides on each other, the blocks fit together, ie they can be arranged side by side, without the film would have to be stretched.
• - As soon as the foils are stacked, each block now has adjacent edges with blocks of the other foil, which lie directly against each other. If you bend the object, the blocks block each other. The rigidity of the object is equivalent to the rigidity of the blocks.
• - The blocks must now resist bending of the object, regardless of the axis of the bend. They are opposed to bending when either one block is on an axis or two blocks share a common edge. On every possible bending axis should now be as many (at least one) blocks and neighboring edges lie, which preclude a bend along this edge. Since the film is not / hardly stretchy, the distance between two blocks will not increase even with a bend along their common edge.
• - By the inventive arrangement of the projections or blocks each foil Biegerungen, along which no blocks or projections are arranged. These bends form a 2D vector base so that each of the two films can be bent in any direction, along each bending direction.
• - In the state of compression, according to the invention, the blocks or projections of the two opposing films arrange in such a way that they block in any possible bending direction.

• - Die Blöcke sollten möglichst regelmäßig angeordnet sein und die Größe und Form aller Blöcke auf einer einzelnen Folie gleich sein. Darüber hinaus soll jeder Block von oben betrachtet eine n-fache Rotationssymmetrie mit möglichst großem n besitzen. Dies ermöglicht, dass die Blöcke auch dann noch ineinander passen, wenn das Objekt im neutralen Zustand verformt wurde. Hierdurch kann das Objekt im neutralen Zustand verfort und mit Unterdruck die neue Form fixiert werden.
• - Die Blöcke sollten so angeordnet werden, dass im Zustand des Unterdrucks ein möglichst geringer Anteil der Folienfläche nicht von ihnen bedeckt wird. Hierdurch wird die maximale Steifigkeit ebenso wie die Riss-Stabilität bei punktuellem Druck auf die Folien erhöht.
• - Die Blöcke sollen eine senkrechte Kante bilden, welche möglichst rechtwinklig zur Folie ist. Hierdurch verkanten sie sich, wenn man die Folie verbiegt. Wenn die Blöcke sich nach oben hin leicht verjüngen, gleiten sie bei Erzeugen des Unterdrucks leichter ineinander, verkanten sich aber weniger effektiv.
• - Die Blöcke sollten möglichst hoch sein, wenn das Objekt besonders steif werden soll. Demgegenüber sollten die Blöcke niedrig bleiben, wenn das Objekt sehr flexibel verbiegbar sein soll.

The described effect of the invention can be improved if the blocks and their arrangements moreover have certain arrangements and characteristics. Among other things, the following advantageous features are possible:

• The blocks should be arranged as regularly as possible and the size and shape of all blocks on a single slide should be the same. In addition, each block is viewed from above have an n-fold rotational symmetry with n as large as possible. This allows the blocks to fit together even if the object has been deformed in the neutral state. As a result, the object can be fixed in the neutral state and with negative pressure the new shape can be fixed.
• - The blocks should be arranged so that in the state of negative pressure as little as possible of the film surface is not covered by them. As a result, the maximum rigidity is increased as well as the crack stability at selective pressure on the films.
• - The blocks should form a vertical edge, which is as perpendicular as possible to the film. As a result, they tilt when bending the film. As the blocks taper slightly upwards, they slide more easily together when the vacuum is created, but they tilt less effectively.
• - The blocks should be as high as possible if the object is to be particularly stiff. In contrast, the blocks should remain low if the object is to be very flexibly bendable.

Using higher blocks increases the maximum rigidity of the object. However, you have to put the blocks further apart, so that each individual foil can still bend. As a result, the blocks must have a higher base area, which reduces the flexibility of the object in the neutral state.

This "dilemma" can be solved by sticking several effectively two-dimensional objects with low blocks on each other. The thickness of the resulting object is thus many times greater, and with it the rigidity in the state of negative pressure.

Advantages of the invention

The invention makes it possible to change the rigidity of an object instantaneously and reversibly. The stiffness in the flexible and stiff state is determined by two completely different materials with different stiffnesses. The stiffness in the neutral and in the state of negative pressure are independent. Therefore, a high maximum rigidity can be achieved even with a small volume. In addition, both materials can be either elastic or viscous as needed. The object according to the invention is insensitive to dirt and moisture, since the high rigidity is not built up by friction. Wear and tear, unlike principles based on friction, are not expected. The effect does not require specific electromagnetic field strengths and temperatures.

embodiment

• 1 schematisch den Aufbau der innenliegenden Oberflächenstrukturen zweier einander zugewandter Folien in perspektivischer und Explosionsansicht,
• 2 und 3 Schnittansichten entlang der Linie II der 1 im geradlinigen Zustand der Folie und im gebogenen Zustand der Folie,
• 4 eine schematische Darstellung des Beutels, bestehend aus zwei Folien im flexiblen Zustand des Beutels,
• 5 eine schematische Darstellung ähnlich der nach 4 jedoch im Zustand des Beutels, in dem dieser nach Art einer Platte geformt und damit versteift ist, und
• 6 und 7

alternative Ausgestaltungen von Objekten mit mehreren Beuteln bzw. mit einem Beutel, der drei Folien und damit sozusagen zwei Kammern aufweist.The invention will be explained in more detail using an exemplary embodiment and with reference to the drawing. In detail, they show:

• 1 1 is a schematic perspective view of the structure of the inner surface structures of two films facing one another, FIG.
• 2 and 3 Sectional views along the line II the 1 in the straight-lined state of the film and in the bent state of the film,
• 4 a schematic representation of the bag, consisting of two films in the flexible state of the bag,
• 5 a schematic representation similar to the 4 but in the state of the bag in which it is shaped and stiffened in the manner of a plate, and
• 6 and 7

alternative embodiments of objects with multiple bags or with a bag that has three foils and thus two chambers so to speak.

The drawing illustrates the principle of action of an object according to the invention 10 , The projections 12 are made of rigid plastic and have the shape of an octahedron ( 1 ). This shape is chosen because it has a high rotational symmetry, has a large edge length and because several octahedra can be uniformly arranged over a large area. Every lead 12 has a width of eg 10 mm (distance between opposite edges) and a height of eg 5 mm ( 2 ).

The projections 12 are glued on a top sheet 14 and one of them separated or by a crease line with the upper foil 14 one-piece and folded back on this lower film 16 , in each case on the mutually facing inner sides 18 these slides 14 . 16 and opposite outer sides 19 (please refer 1 ), with the slides 14 . 16 have a low rigidity against bending and a low elasticity. On every slide 14 . 16 are the tabs 12 arranged in rows. Along one row have two adjacent protrusions 12 a distance equal to the width of a projection. This can be any slide 14 . 16 , such as 3 shows, bend. Two adjacent rows of protrusions 12 are about a head start 12 arranged so that even between two adjacent rows never two projections 12 a slide 14 . 16 touch. This leads to every slide 14 . 16 to a pattern of protrusions 12 and spaces 20 and thus to a surface structure 22 , which has projections and recesses arranged as on a chessboard ( 1 ). There are no square projections 12 used, so that the smallest distance from each other having projections 12 ie the "nearest neighbors" of the projections 12 every slide 14 . 16 still have a distance of a maximum of a projection height and the projections 12 at a bending of the films 14 . 16 do not block along their diagonals.

The upper and the lower foil 14 . 16 are at their edges 24 welded together and form an airtight bag 26 (please refer 4 and 5 ). About an opening 28 leads a hose 30 in the bag 26 , allowing air out of the bag 26 over eg sucked a pump and on the other hand air in the bag 26 can be admitted.

In the neutral state (air in the bag) the projections grip 12 not in each other ( 4 ). So you can get the slides 14 . 16 along the edges of the projections 12 bend with little force. Once you have a negative pressure in the bag 26 generated, the projections engage 12 into each other and form a stiff plate with very high filling (material density), such as 5 shows. Bending is not possible in this state, even with great effort, since the high rigidity having protrusions 12 block each other.

In the 5 and 6 Two alternative embodiments of a variable stiffness object according to the invention are shown. In 6 assigns the object 10 ' two or more stacked bags 26 ' on, which are either ventilated individually or via a distributor 32 ' be ventilated or ventilated together.

In 7 an embodiment is shown in which the object 10 " a bag 26 " with two chambers 34 " having. To every chamber 34 " introduces a ventilation hose, leaving the two chambers 34 " either separately or via a distributor 32 " can be simultaneously ventilated and vented. The bag 26 " indicates as above using the 1 to 5 described the two slides 14 . 16 and additionally a middle foil 36 " on. The opposing surfaces of the two film pairs formed thereby from the upper film and the middle film as well as the middle film and the lower film are with the complementarily formed surface structures 22 from protrusions 12 and spaces 20 provided as above related to the 1 to 6 is described.

Finally, it should be noted that several double or multi-chamber bag 26 " , as in 7 shown, can be arranged one above the other. Also, the different bag types of the 6 and 7 to be combined into an object. When using multiple bags they are firmly connected together along their respective superimposed films (for example, glued).

application areas

The invention describes a principle which instantaneously increases or decreases the stiffness of a planar object from bending, i. can change. By deforming the basic planar object, stiffness changes along other axes are also possible. If you create an object in which the planar surface is folded several times in zigzag, you have a spring with changeable stiffness. The folded object can be squeezed from above either lightly or hard.

When the two foils are formed as a double-walled tube, a negative pressure affects the stiffness in bending along a transverse axis of the tube. The tube is light or unbendable depending on the condition. This could be interesting for operation robots that are used for minimally invasive surgery. These usually consist of long rods or hoses. In order to introduce them into the body, a high degree of flexibility is required so that the robot can move around internal body structures. Once the tissue to be operated is achieved, high rigidity is required to work precisely and apply high forces and torques.

Also conceivable is a windshield for cars, which consists of two transparent films and blocks of glass or transparent plastic. The normal condition here would be the condition of negative pressure, so that the windscreen is stiff in operation and visibility is clear. Once an accident, e.g. With a pedestrian detected, the vacuum would be released. This can happen passively by a sting in the air bag, but also by actively inflating the air bag as in an air bag. The windshield would be flexible. As a result, the impact of the pedestrian or a possibly unbolted car occupant would be cushioned on the windshield. If the car then had to be opened by force, rescue workers could easily cut open the foil of the windshield with little force. Unlike the impact of a windshield this would not be broken glass, which endanger the rescue or the car occupants.

Further fields of application would be articles which, in use, must be stiff but flexible for transport, e.g. Protectors in sports, folding kayaks or camping furniture, protective shields etc.

BIBLIOGRAPHY

• [1] M. Yalcintas and H. Dai, "Magnetorheological and electrorheological materials in adaptive structures and their performance comparison", Smart Materials and Structures, vol. 8, no. 5, p. 560, 1999 , [On-line]. Available: http://stacks.iop.org/0964-1726/8/i=5/a=306
• [2] C. Laschi and M. Cianchetti, "Soft Robotics: New perspectives for robot bodyware and control", Frontiers in Bioengineering and Biotechnology, vol. 2, p. 3, 2014 , [ On-line]. Available: http://journal.frontiersin.org/article/10.3389/fbioe.2014.00003
• [3] YJ Kim, S. Cheng, S. Kim, and K. Iagnemma, "A novel layer of jamming mechanism with tunable stiffness capability for minimally invasive surgery", IEEE Transactions on Robotics, vol. 29, no. 4, pp. 1031-1042, Aug 2013 ,
• [4] N. Cheng, G. Ishigami, S. Hawthorne, H. Chen, M. Hansen, M. Telleria, R. Playter, and K. Iagnemma, "Design and analysis of a soft mobile robot composed of multiple thermally activated joints driven by a single actuator ", 2010 IEEE International Conference on Robotics and Automation, May 2010 , pp. 5207-5212.
• [5] AJ Loeve, OS van de Ven, JG Vogel, P. Breedveld, and J. Dankelman, "Vacuum packed particles as flexible endoscope guides with controllable rigidity," Granular Matter, vol. 12, no. 6, pp. 543-554, 2010 , [On-line]. Available: http://dx.doi.org/10.1007/sl0035-010-0193-8
• [6] S. Zuo, N. Ymanaka, K. Masamune, H. Liao, K. Matsumiya, and T. Dohi, MRI Compatible Rigid-Flexible Outer Sheath Device Using Pneumatic Locking Mechanism for Endoscopic Treatment. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008 , pp. 741-744. [On-line]. Available: http://dx.doi.org/10.1007/978-3-540-79039-6 183
• [7] Jamming as an enabling technology for soft robotics, vol. 7642, 2010. [Online]. Available: http://dx.doi.org/10.1117/12.853182
• [8th] J. Ou, L. Yao, D. Tauber, J. Steimle, R. Niiyama, and H. Ishii, "jamsheets: thin interfaces with tunable stiffness enabled by layer jamming", in Proceedings of the 8th International Conference on Tangible, Embedded and Embodied Interaction, ser. TEI '14. New York, NY, USA: ACM, 2013, pp. 65-72 , [On-line]. Available: http://doi.acm.org/10.1145/2540930.2540971
• [9] S. Zuo, T. Ohdaira, K. Kuwana, Y. Nagao, S. Ieiri, M. Hashizume, T. Dohi, and K. Masamune, Developing Essential Rigid-Flexible Outer Sheath to Enable Novel Multi-piercing Surgery. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012, pp. 26-33 , [On-line]. Available: http://dx.doi.org/10.1007/978-3-642-33415-3 4

LIST OF REFERENCE NUMBERS

10

object

10 '

object

10 "

object

12

head Start

14

upper foil

16

lower foil

18

inside

19

outside

20

interspaces

22

surface structure

24

margins

26

Single or multi-chamber bag

28

opening

30

tube

32 '

distributor

32 "

distributor

34 "

chamber

36 "

middle foil

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2011/079865 A1 [0012]
• US 2015/0369325 A1 [0012]
• WO 2016/100174 A1 [0018]
• WO 2016/100182 Al [0018]

Cited non-patent literature

• M. Yalcintas and H. Dai, "Magnetorheological and electrorheological materials in adaptive structures and their performance comparison", Smart Materials and Structures, vol. 8, no. 5, p. 560, 1999 [0059]
• C. Laschi and M. Cianchetti, "Soft Robotics: New perspectives for robot bodyware and control", Frontiers in Bioengineering and Biotechnology, vol. 2, p. 3, 2014 [0059]
• Y.J. Kim, S. Cheng, S. Kim, and K. Iagnemma, "A novel layer jamming mechanism with tunable stiffness capability for minimally invasive surgery", IEEE Transactions on Robotics, vol. 29, no. 4, pp. 1031-1042, Aug 2013 [0059]
• N. Cheng, G. Ishigami, S. Hawthorne, H. Chen, M. Hansen, M. Telleria, R. Playter, and K. Iagnemma, "Design and analysis of a soft mobile robot composed of multiple thermally activated joints driven by a single actuator ", 2010 IEEE International Conference on Robotics and Automation, May 2010 [0059]
• A.J. Loeve, O.S. van de Ven, J.G. Vogel, P. Breedveld, and J. Dankelman, "Vacuum packed particles as flexible endoscope guides with controllable rigidity," Granular Matter, vol. 12, no. 6, pp. 543-554, 2010 [0059]
• S. Zuo, N. Ymanaka, K. Masamune, H. Liao, K. Matsumiya, and T. Dohi, MRI Compatible Rigid-Flexible Outer Sheath Device Using Pneumatic Locking Mechanism for Endoscopic Treatment. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008 [0059]
• J. Ou, L. Yao, D. Tauber, J. Steimle, R. Niiyama, and H. Ishii, "jamsheets: thin interfaces with tunable stiffness enabled by layer jamming", in Proceedings of the 8th International Conference on Tangible, Embedded and Embodied Interaction, ser. TEI '14. New York, NY, USA: ACM, 2013, pp. 65-72 [0059]
• S. Zuo, T. Ohdaira, K. Kuwana, Y. Nagao, S. Ieiri, M. Hashizume, T. Dohi, and K. Masamune, Developing Essential Rigid-Flexible Outer Sheath to Enable Novel Multi-piercing Surgery. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012, pp. 26-33 [0059]

Claims (13)

Variable stiffness object, with at least two foils (14, 16), which are arranged one above the other and have inner sides (18) facing one another and outer sides (19) facing away from one another, - Wherein the distance between the two films (14,16) is variable by generating a negative pressure within an inner volume located between the two films (14,16) and / or by generating an overpressure in an outer volume located outside of the films (14,16) . - wherein on the inside (18) of the first film (14) a first surface structure (22) of a first array of a plurality of on the inside (18) of the first film (14) fixed, raised first projections (12) with between these arranged first intermediate spaces (20) which are each surrounded by at least three first projections (12) arranged and / or formed, - wherein on the inside (18) of the second film (16) a second surface structure (22) of a second array of a plurality of on the inside (18) of the second film (16) fixed, raised second projections (12) with between these arranged second intermediate spaces (20), which are each surrounded by a plurality of second projections (12), arranged and / or is formed, and - wherein a first projection (12) of the first surface structure (22) on the inside (18) of the first film (14) reducing the distance between the two films (14,16) in the said second projection (12) associated second intermediate space ( 20) of the second surface structure (22) on the inner side (18) of the second film (16) and thereby at least three second outer space (20) limiting second projections (12) of the second surface structure (22) of the inner side (18) the second foil (16) rests. Object after Claim 1 , characterized in that the distance of the projections (12) of the surface structure (22) of the inside (18) of each film (14,16) is at least equal to the height of the projections (12). Object after Claim 1 or 2 , characterized in that the projections (12) of the surface structure (22) of the inside (18) of each film (14,16) or per individual film (14,16) have the same geometry. Object after one of Claims 1 to 3 , characterized in that the projections (12) of the surface structure (22) of the inner side (18) of each film (14,16) or per individual film (14,16) are arranged regularly. Object after one of Claims 1 to 4 , characterized in that each projection (12) when viewing the inside (18) of a film (14,16) in the extension of the normal on this inside (18) standing n-fold rotational symmetry, where n is greater than three or greater than is four or greater than six or greater than eight, or wherein the projections (12) in the plan view of the surface structure are in particular triangular, square or hexagonal. Object after one of Claims 1 to 5 characterized in that each projection (12) has a peripheral peripheral surface which projects at an angle of substantially 90 ° from the inside (18) of the film (14, 16) and in that a projection (12) in the state it is immersed in its associated space (20), the peripheral surface of a gap (20) limiting this projection (12) and preferably the peripheral surfaces of all this gap (20) delimiting projections (12) contacted. Object after one of Claims 1 to 6 characterized in that each projection (12) has a circumferential peripheral surface with a plurality of adjacent planar surface portions, each two adjacent planar surface portions forming an angle of less than 180 °, and that a projection (12) in the state in which it immersed in the intermediate space (20) assigned to it, makes contact with a surface section of a projection (12) surrounding this intermediate space (20) and preferably in each case a surface section of all projections (12) bounding this intermediate space (20). Object after one of Claims 1 to 7 , characterized in that a plurality of pairs of films each of a first film (14) and a second film (16) are arranged one above the other, wherein the outer side (19) of a film (14) of a pair of films on the outer side (19) of a film (16) of the adjacent film pair is applied and these two films (14,16) connected to each other, in particular glued. Object after one of Claims 1 to 7 , characterized by at least one third film (36 ") arranged between the first and the second film (14, 16), the at least one third film (36") each having on its two main sides a surface structure (22) of one An array of a plurality of raised projections (12) fixed on the respective main side of the third film (36 ") with interspaces (20) arranged between them, which are each surrounded by a plurality of projections (12), and wherein the respective surface structure ( 22) of the at least one third film (36 ") is complementary to the respective surface structure (22) of the respective main side of the third film (36") opposite the inside (18) of the first and second film (14,16) or the opposite main side of another third film (36 "). Object after one of Claims 1 to 9 , characterized in that the first and the second film (16) each having an outer edge, along which the two films (14,16) to form a first bag (26) are connected to each other in a gastight manner, and that the bag (26) a closable opening (28) for ventilation of the inner volume of the bag (26) is provided. Object after one of Claims 1 to 10 , characterized in that each first, second and, if present, third film (36 ") has an outer edge, each adjacently arranged films (14,16) to form a respective bag (26) along its outer edges (24) connected in a gastight manner are, and that each bag (26) with a closable opening (28) for ventilation of the bag (26) is provided. Object after one of Claims 1 to 11 , characterized in that the first surface structure (22) is complementary to the second surface structure at least in partial areas or over its entire surface area. Object after one of Claims 1 to 12 , characterized in that the projections (12) project directly from the film (14,16) and that the films (14,16) form the bottoms of the intermediate spaces (20).

Images